Apple:

Now you can add money directly to your iTunes or App Store account with iTunes Pass. To get iTunes Pass, go to the iTunes Store on your iOS device, scroll down, and tap the Redeem button. Then go in to any Apple Retail Store and let a Specialist know you want to add credit to your account. Open iTunes Pass in Passbook, and have the Specialist scan it and accept your payment. Your balance will be updated and can be used immediately.

This might be slightly more convenient than buying physical gift cards for yourself but is it a service you’ll actually use?